This invention relates to lubricating oil compositions, their method of preparation, and use. More specifically, this invention relates to lubricating oil compositions containing an alkylated diphenylamine, a sulfurized olefin/fatty oil and/or an ashless dialkyldithiocarbamate, and an alkylated phenothiazine. The lubricating oil compositions of this invention are particularly useful as crankcase lubricants.
Lubricating oils as used in the internal combustion engines and transmissions of automobiles or trucks are subjected to a demanding environment during use. This environment results in the oil suffering oxidation which is catalyzed by the presence of impurities in the oil, such as iron compounds, and is also promoted by the elevated temperatures of the oil during use.
The oxidation of lubrication oils during use is usually controlled to some extent by the use of antioxidant additives which may extend the useful life of the lubricating oil, particularly by reducing or preventing unacceptable viscosity increases. Aminic antioxidants are antioxidants that contain one or more nitrogen atoms. An example of an aminic antioxidant is phenothiazine. The prior art discloses the many teachings on the synthesis and uses of phenothiazine. Phenothiazine antioxidants have been used as a stand alone additive, chemically modified or grafted onto the backbone of polymers.
A new trend in engine oils is a shift to lower and lower phosphorus levels. Thus, at some point the industry will require lubricant formulations for crankcase with significantly lower, zero or essentially zero phosphorus content.
Existing lubricants employing phenothiazine are taught in U.S. Pat. No. 5,614,124 and references cited therein, all of which are incorporated herein in their entirety by reference.
Existing lubricants employing alkylated diarylamine and a sulfurized compound are taught in U.S. Pat. Nos. 5,840,672, 6,174,842, 6,326,336, and references cited therein, all of which are incorporated herein in their entirety by reference.
U.S. Pat. No. 2,781,318 teaches the synthesis and use of dialkylphenothiazines as an oil soluble ashless detergent additive for mineral lubricating oils. The alkylation is on the aromatic ring and each alkyl group contains 4 to 16 carbons.
U.S. Pat. No. 3,536,706 teaches the use of branched mono-alkylated alkylphenothiazine as an antioxidant additive for synthetic lubricants. The alkyl groups contain 4 to 12 carbons.
U.S. Pat. No. 4,072,619 teaches the use of nitrogen substituted polyoxyalkylene phenothiazines for use in synthetic motor oils.
U.S. Pat. No. 5,073,278 teaches a lubricant composition containing an aromatic amine and a sterically hindered amine. The aromatic amine can be a ring-substituted alkylphenothiazine or nitrogen substituted alkylated phenothiazine.
U.S. Pat. No. 5,157,118 teaches the nitrogen substitution of a phenothiazine where the nitrogen substitutent contains an additional sulfur atom.
U.S. Pat. No. 5,200,100 teaches the grafting of a monomer onto the backbone of an E-P polymer. The monomer contains an aminoalkylphenothiazine moiety.
U.S. Pat. No. 5,503,759 teaches the alkylation of mixtures of diphenylamine, alkyldiphenylamines, phenothiazine and alkylphenothiazines with an olefin in the presence of an acid catalyst.
U.S. Pat. No. 5,167,844 teaches a lubricant formulation containing at lease three additives to guard against oxidative degradation. These three additives are: alkali metal dialkyl dithiophosphates, an aromatic amine such as an alkylphenothiazine and a compound from either a sterically hindered amine, acyclic sterically hindered amine or alkylphenols.
The aforementioned patents are hereby incorporated by reference.
In broadest terms, a lubricating composition of the present invention comprises a major amount of lubricating oil, and a minor amount of an oil soluble alkylated diarylamine, an oil soluble alkylated phenothiazine, and an oil soluble sulfurized compound. It is preferred that the sulfurized compound is selected from the group consisting of sulfurized olefins, and sulfurized fatty oils. A second lubricating composition of the present invention comprises a major amount of lubricating oil, and a minor amount of an oil soluble alkylated diarylamine, an oil soluble alkylated phenothiazine, and an oil soluble ashless dialkyldithiocarbamate.
While any conventional or non-conventional lubricating oil may be used in the present invention, it is preferred that the lubricating oil is selected from the group consisting of paraffinic oils, naphthenic oils, aromatic oils, and synthetic oils and mixtures thereof.
The concentration of the alkylated diarylamine may range from about 0.001 to 10 wt % in the lubricating composition, however, it is preferred that the concentration range from about 0.05 to 2.5 wt % in the lubricating composition.
It is preferred that the alkylated diarylamine is selected from the group consisting of: diphenylamine, alkylated diphenylamine, 3-hydroxydiphenylamine, N-phenyl-1,2-phenylenediamine, N-phenyl-1,4-phenylenediamine, monobutyldiphenylamine, dibutyldiphenylamine, monooctyldiphenylamine, dioctyldiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monotetradecyldiphenylamine, ditetradecyldiphenylamine, phenyl-alpha-naphthylamine, monooctyl phenyl-alpha-naphthylamine, phenyl-beta-naphthylamine, monoheptyldiphenylamine, diheptyldiphenylamine, p-oriented styrenated diphenylamine, mixed butyloctyidiphenylamine, and mixed octylstryryldiphenylamine.
The concentration of the alkylated phenothiazine may range from about 0.001 to 10 wt % in the lubricating composition, however, it is preferred that the concentration range from about 0.05 to 2.5 wt % in the lubricating composition.
It is further preferred that the alkylated phenothiazine have the chemical formula: 
wherein R1 is a linear or branched C4-C24 alkyl, aryl, heteroalkyl or alkylaryl group and R2 is hydrogen or a linear or branched C4-C24 alkyl, aryl, heteroalkyl, or alkylaryl group.
It is even more preferred that the alkylated phenothiazine is selected from the group consisting of monotetradecylphenothiazine, ditetradecylphenothiazine, monodecylphenothiazine, didecylphenothiazine, monononylphenothiazine, dinonylphenothiazine, monoctylphenothiazine, dioctylphenothiazine, monobutylphenothiazine, dibutylphenothiazine, monostyrylphenothiazine, distyrylphenothiazine, butyloctylphenothiazine, and styryloctylphenothiazine.
While the sulfurized compound may be present in sufficient concentration so as to provide from about 25 to 5000 ppm of sulfur in the lubricating composition, it is preferred that the sulfurized compound be present in a concentration sufficient to provide from about 150 to 2500 ppm of sulfur in the lubricating composition.
It is preferred that the sulfurized olefin is selected from the group consisting of sulfurized C4-C24 alpha-olefins, sulfurized isomerized C4-C24 alpha-olefins, sulfurized branched C4-C24 olefins, sulfurized cyclic C4-C24 olefins, HITEC(copyright) 7084, HITEC(copyright) 7188, HITEC(copyright) 312, ADDITIN RC 2540-A, and combinations thereof. HiTEC(copyright) is a registered trademark of Ethyl Corporation.
It is preferred that the sulfurized fatty oil is selected from the group consisting of sulfurized corn oil, sulfurized canola oil, sulfurized cottonseed oil, sulfurized grapeseed oil, sulfurized olive oil, sulfurized palm oil, sulfurized peanut oil, sulfurized coconut oil, sulfurized rapeseed oil, sulfurized sesame seed oil, sulfurized soybean oil, sulfurized sunflower seed oil, sulfurized tallow, sulfurized fish oil including herring oil and sardine oil, ADDITIN R 4410, ADDITIN R 4412-F, ADDITIN R 4417, ADDITIN RC 2515, ADDITIN RC 2526, ADDITIN RC 2810-A, ADDITIN RC 2814-A, ADDITIN RC 2818-A, and combinations thereof. ADDITIN(copyright) is a registered trademark of Rhein Chemie Corporation.
It is preferred that the ashless dialkyldithiocarbamate have a concentration sufficient to provide from about 150 to 2500 ppm of sulfur in the lubricating composition. It is further preferred that the ashless dialkyldithiocarbamate is selected from the group consisting of: methylenebis(dialkyldithiocarbamate), ethylenebis(dialkyldithiocarbamate), isobutyl disulfide-2,2xe2x80x2-bis(dialkyld ithiocarbamate), dibutyl-N,N-dibutyl-(d ithiocarbamyl)succinate, 2-hydroxypropyl dibutyidithiocarbamate, butyl(dibutyid ithiocarbamyl)acetate, S-carbomethoxy-ethyl-N,N-dibutyl dithiocarbamate, hydroxyalkyl substituted dialkyldithiocarbamates, dithiocarbamates prepared from unsaturated compounds, dithiocarbamates prepared from norbornylene, and dithiocarbamates prepared from epoxides, and mixtures and precursors thereof.
Additionally, the lubricating composition of the present invention may comprise at least one additional component selected from the group consisting of: dispersants, detergents, anti-wear additives, antioxidants, friction modifiers, anti-foaming additives, pour point depressants, and viscosity index improvers.
Irrespective of composition, it is preferred that the lubricating composition have a low phosphorus content or be substantially devoid of phosphorus. By xe2x80x9chave a low phosphorus contentxe2x80x9d herein is meant a level between 250 ppm and 900 ppm phosphorus. Byxe2x80x9csubstantially devoid of phosphorusxe2x80x9d herein is meant a level of less than about 250 ppm. It is most preferred that the lubricating composition comprises zero phosphorus.
The lubricating composition of the present invention may also comprise two sulfurized compounds where one represents sulfurized olefins and/or sulfurized fatty oils, and the other represents ashless dialkyldithiocarbamates as defined above.
A lubricating additive of the present invention comprises an oil soluble alkylated diarylamine, an oil soluble alkylated phenothiazine, and an oil soluble sulfurized compound. The sulfurized compound is preferably selected from the group consisting of sulfurized olefins and sulfurized fatty oils. The lubricating additive forms a lubricating composition when added to a lubricating oil.
A second lubricating additive of the present invention comprises an oil soluble alkylated diarylamine, an oil soluble alkylated phenothiazine, and an ashless dialkyldithiocarbamate. The lubricating additive forms a lubricating composition when added to a lubricating oil.
The lubricating additive may also comprise two sulfurized compounds where one represents sulfurized olefins and/or sulfurized fatty oils, and the other represents ashless dialkyldithiocarbamates as defined above.
A method for improving the antioxidancy and/or deposit formation properties of a lubricating composition of the present invention comprises the step of including in the lubricating composition an oil soluble alkylated diarylamine, an oil soluble alkylated phenothiazine, and an oil soluble sulfurized compound. The sulfurized compound is preferably selected from the group consisting of sulfurized olefins and sulfurized fatty oils.
A second method for improving the antioxidancy and/or deposit formation properties of a lubricating composition of the present invention comprises the step of including in the lubricating composition an oil soluble alkylated diarylamine, an oil soluble alkylated phenothiazine, and an oil soluble ashless dialkyldithiocarbamate.
While the sulfurized compound used in the methods of the present invention may be present in sufficient concentration so as to provide from about 25 to 5000 ppm of sulfur in the lubricating composition, it is preferred that the sulfurized compound be present in a concentration sufficient to provide from about 150 to 2500 ppm of sulfur in the lubricating composition.
It is preferred that the sulfurized olefin used in the methods of the present invention is selected from the group consisting of sulfurized C4-C24 alpha-olefins, sulfurized isomerized C4-C24 alpha-olefins, sulfurized branched C4-C24 olefins, sulfurized cyclic C4-C24 olefins, HITEC(copyright) 7084, HITEC(copyright) 7188, HITEC(copyright) 312, ADDITIN RC 2540-A, and combinations thereof.
It is preferred that the sulfurized fatty oil used in the methods of the present invention is selected from the group consisting of sulfurized corn oil, sulfurized canola oil, sulfurized cottonseed oil, sulfurized grapeseed oil, sulfurized olive oil, sulfurized palm oil, sulfurized peanut oil, sulfurized coconut oil, sulfurized rapeseed oil, sulfurized sesame seed oil, sulfurized soybean oil, sulfurized sunflower seed oil, sulfurized tallow, sulfurized fish oil including herring oil and sardine oil, ADDITIN R 4410, ADDITIN R 4412-F, ADDITIN R 4417, ADDITIN RC 2515, ADDITIN RC 2526, ADDITIN RC 2810-A, ADDITIN RC 2814-A, ADDITIN RC 2818-A, and combinations thereof.
The concentration of the alkylated diarylamine used in the methods of the present invention may range from about 0.001 to 10 wt % in the lubricating composition, however, it is preferred that the concentration range from about 0.05 to 2.5 wt % in the lubricating composition.
It is preferred that the alkylated diarylamine used in the methods of the present invention is selected from the group consisting of: diphenylamine, alkylated diphenylamine, 3-hydroxydiphenylamine, N-phenyl-1,2-phenylenediamine, N-phenyl-1,4-phenylenediamine, monobutyldiphenylamine, dibutyidiphenylamine, monooctyldiphenylamine, dioctyidiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monotetradecyldiphenylamine, ditetradecyldiphenylamine, phenyl-alpha-naphthylamine, monooctyl phenyl-alpha-naphthylamine, phenyl-beta-naphthylamine, monoheptyldiphenylamine, diheptyldiphenylamine, p-oriented styrenated diphenylamine, mixed butyloctyldiphenylamine, and mixed octylstryryldiphenylamine.
The concentration of the alkylated phenothiazine used in the methods of the present invention may range from about 0.001 to 10 wt % in the lubricating composition, however, it is preferred that the concentration range from about 0.05 to 2.5 wt % in the lubricating composition.
It is further preferred that the alkylated phenothiazine have the chemical formula: 
wherein R1 is a linear or branched C4-C24 alkyl, aryl, heteroalkyl or alkylaryl group and R2 is hydrogen or a linear or branched C4-C24 alkyl, heteroalkyl, or alkylaryl group.
It is even more preferred that the alkylated phenothiazine is selected from the group consisting of monotetradecylphenothiazine, ditetradecylphenothiazine, monodecylphenothiazine, didecylphenothiazine, monononylphenothiazine, dinonylphenothiazine, monoctylphenothiazine, dioctylphenothiazine, monobutylphenothiazine, dibutylphenothiazine, monostyrylphenothiazine, distyrylphenothiazine, butyloctylphenothiazine, and styryloctylphenothiazine.
While the ashless dialkyldithiocarbamate used in the methods of the present invention may be present in sufficient concentration so as to provide from about 25 to 5000 ppm of sulfur in the lubricating composition, it is preferred that the ashless dialkyldithiocarbamate be present in a concentration sufficient to provide from about 150 to 2500 ppm of sulfur in the lubricating composition.
It is preferred that the ashless dialkyldithiocarbamate used in the methods of the present invention is selected from the group consisting of: methylenebis(dialkyldithiocarbamate), ethylenebis(dialkyldithiocarbamate), isobutyl disulfide-2,2xe2x80x2-bis(dialkyldithiocarbamate), dibutyl-N,N-dibutyl-(dithiocarbamyl)succinate, 2-hydroxypropyl dibutyidithiocarbamate, butyl(dibutyldithiocarbamyl)acetate, S-carbomethoxy-ethyl-N,N-dibutyl dithiocarbamate, hydroxyalkyl substituted dialkyldithiocarbamates, dithiocarbamates prepared from unsaturated compounds, dithiocarbamates prepared from norbornylene, and dithocarbamates prepared from epoxides.
The methods of the present invention may also comprise the step of including two sulfurized compounds where one represents sulfurized olefins and/or sulfurized fatty oils, and the other represents ashless dialkyldithiocarbamates as defined above.
The methods may additionally comprise the step of including at least one additional component in said lubricating composition. It is preferred that at least one additional component is selected from the group consisting of: dispersants, detergents, anti-wear additives, antioxidants, friction modifiers, anti-foaming additives, pour point depressants, and viscosity index improvers.
In accordance with the foregoing summary, the following presents a detailed description of the preferred embodiment of the invention that are currently considered to be the best mode.
We shall begin with a discussion of the components used in the present invention and conclude with a discussion of prepared additized test oils and their comparative results.
The diarylamines useful in this invention are well known antioxidants and there is no particular restriction on the type of diarylamine that can be used. Preferably, the diarylamine has the formula: 
Wherein Rxe2x80x2 and Rxe2x80x3 each independently represents a substituted or unsubstituted aryl group having from 6 to 30 carbon atoms. Illustrative of substituents for the aryl group include aliphatic hydrocarbon groups such as alkyl having from 1 to 30 carbon atoms, hydroxy groups, halogen radicals, carboxylic acid or ester groups, or nitro groups. The aryl is preferably substituted or unsubstituted phenyl or naphthyl, particularly wherein one or both of the aryl groups are substituted with at least one alkyl having from 4 to 30 carbon atoms, preferably from 4 to 18 carbon atoms, most preferably from 4 to 9 carbon atoms. It is preferred that one or both aryl groups be substituted, e.g. mono-alkylated diphenylamine, di-alkylated diphenylamine, or mixtures of mono- and di-alkylated diphenylamines.
The diarylamines used in this invention can be of a structure other than that shown in the above formula that shows but one nitrogen atom in the molecule. Thus the diarylamine can be of a different structure provided that at least one nitrogen has 2 aryl groups attached thereto, e.g. as in the case of various diamines having a secondary nitrogen atom as well as two aryls on one of the nitrogens.
The diarylamines used in this invention should be soluble in the formulated crankcase oil package. Examples of some diarylamines that may be used in this invention include: diphenylamine; various alkylated diphenylamines; 3-hydroxydiphenylamine; N-phenyl-1,2-phenylenediamine; N-phenyl-1,4-phenylenediamine; monobutyldiphenylamine; dibutyldiphenylamine; monooctyldiphenylamine; dioctyldiphenylamine; monononyidiphenylamine; dinonyldiphenylamine; monotetradecyldiphenylamine; ditetradecyldiphenylamine, phenyl-alpha-naphthylamine; monooctyl phenyl-alpha-naphthylamine; phenyl-beta-naphthylamine; monoheptyldiphenylamine; diheptyldiphenylamine; p-oriented styrenated diphenylamine; mixed butyloctyldiphenylamine; and mixed octylstryryldiphenylamine.
Examples of commercial diarylamines include, for example, IRGANOX L06, IRGANOX L57 and IRGANOX L67 from Ciba Specialty Chemicals; NAUGALUBE AMS, NAUGALUBE 438, NAUGALUBE 438R, NAUGALUBE 438L, NAUGALUBE 500, NAUGALUBE 640, NAUGALUBE 680, and NAUGARD PANA from Crompton Corporation; GOODRITE 3123, GOODRITE 3190X36, GOODRITE 3127, GOODRITE 3128, GOODRITE 3185X1, GOODRITE 3190X29, GOODRITE 3190X40, GOODRITE 3191 and GOODRITE 3192 from BF Goodrich Specialty Chemicals; VANLUBE DND, VANLUBE NA, VANLUBE PNA, VANLUBE SL, VANLUBE SLHP, VANLUBE SS, VANLUBE 81, VANLUBE 848, and VANLUBE 849 from R. T. Vanderbilt Company Inc.
An alkylated phenothiazine suitable for this invention must be oil soluble and correspond to the general formula wherein R1 is a linear or branched C4-C24 alkyl, aryl, heteroalkyl or alkylaryl group and R2 is H or a linear or branched C4-C24 alkyl, aryl, heteroalkyl or alkylaryl group. 
Typical examples of alkylphenothiazine are monotetradecylphenothiazine, ditetradecylphenothiazine, monodecylphenothiazine, didecylphenothiazine. monononylphenothiazine, dinonylphenothiazine, monoctylphenothiazine and dioctylphenothiazine.
Non-limiting examples of the preparation of alkylphenothiazine are mentioned in U.S. Pat. Nos. 5,614,124 and 2,781,318, each incorporated herein by reference.